Use USB Flash Memory sold by Roland.
Other products are not guaranteed to work.

* 0dBu=0.775Vrms

*In the interest of product
improvement, the specifications and/or appearance of this unit are
subject to change without prior notice.

*1: When a REAC Splitter S-4000D or a
switching hub is used in-line with REAC cables, the network latency
will increase by the amount of processing delay introduced by the
splitting device itself. The actual delay is dependant upon the
specifications of the splitting device, though the maximum delay
amount for a single splitting device should be no more than 200
microseconds.